I think it may be that particular screenset, I have just tested your code on 4 different Mach3 screensets and 2 different Mach4 screensets and it works on all of them, next I tried the 2010 screenset and I get the same issues as you so try a different screenset, the default 1024 screenset would be a good place to start, I found the 2010 one to be unstable and that was on a PC with XP Pro 32 bit OS which runs anything and everything
Regards
Rob"
Not sure why its not running...using mach 3. This line flashes red in the readout and then nothing...just sits there...